1. Field of the Invention
The present invention relates to phosphor ink, and in particular to a method for making phosphor ink and a system using the same.
2. Description of the Related Art
In general, a printing technique using an ink jet system implements an expected image by discharging ink through nozzles, and accordingly unnecessary consumption of materials can be reduced. In addition, the printing technique can implement an image having high resolution by adjusting intervals of the nozzles, and accordingly applying it to display panels for various displays has been examined. In particular, applying it to a phosphor spreading method for a PDP (plasma display panel) has been examined.
In the PDP, because an inorganic phosphor having an average particle's diameter of 1 μm˜10 μm is used as a luminous body, it is very important to use a technique for making phosphor ink in which the inorganic particles are uniformly dispersed.
Hereinafter, a method for making phosphor ink in accordance with the conventional art will be described with reference to FIG. 1.
FIG. 1 shows a method for making phosphor ink in accordance with the conventional art.
As depicted in FIG. 1, in the conventional method for making phosphor ink, by rubbing mechanically or colliding physically inorganic phosphor 11 (inorganic phosphor particles) mixed in a specific mixed liquor 10 against a ball 12 of a ball mill (not shown) or a dispersing agent 13 or a binder 14, etc., the inorganic phosphor 11 is dispersed in the mixed liquor 10, and accordingly phosphor ink can be obtained. Herein, by the ball 12 of the ball mill used in the conventional phosphor ink making method, because a size of each particle of the inorganic phosphor 11 can be reduced, the inorganic phosphor 11 can be passed a nozzle easily, and accordingly spray characteristics of the inorganic phosphor ink can be improved.
However, in the conventional method for making phosphor ink, when the inorganic phosphor 11 is dispersed in the mixed liquor 10, by friction between the particle with the ball of the ball mill or among the particles, a surface defect layer 20 is induced on the surfaces of particles of the inorganic phosphor 11. The surface defect layer 20 formed on the particle surface of the inorganic phosphor 11 will be described with reference to FIG. 2.
FIG. 2 illustrates the surface defect layer formed on the particle of the inorganic phosphor in accordance with the conventional art.
As depicted in FIG. 2, the surface defect layer 20 formed on the inorganic phosphor 11 reduces light generated in the phosphor, and accordingly radiating efficiency of a PDP using the phosphor is remarkably lowered. After a time for dispersing the inorganic phosphor 11 in the mixed liquor 10 has passed, a quantity of light generated in the phosphor is remarkably reduced. Hereinafter, radiating efficiency reduction of the phosphor caused by the surface defect layer 20 formed on the particle surface of the phosphor and a luminance lowering phenomenon caused by that will be described with reference to FIG. 3.
FIG. 3 is a graph illustrating the luminance lowering phenomenon caused by the surface defect layer formed on the particle surface of the phosphor.
As depicted in FIG. 3, the more a time for dispersing the inorganic phosphor particles in the mixed liquor 11 has passed, a size of an inorganic phosphor particle 11 gets smaller, because of that, spray characteristics can be improved. However, because the surface defect layer 20 formed on the particle surface of the phosphor 11 is increased, a quantity of light generated in the inorganic phosphor is reduced due to the surface defect layer 20, and accordingly luminance of the PDP is lowered. In more detail, when phosphor ink is made of inorganic phosphor particles having surface defect layers and a phosphor layer of a PDP is fabricated with that phosphor ink, luminance of the PDP is lowered due to the surface defect layers 20.
As described-above, in the method for making phosphor ink in accordance with the conventional art, a surface defect layer may be formed on the particle surface of the phosphor, a quantity of light generated in the phosphor may be reduced due to the surface defect layer, and accordingly luminance of a PDP may be lowered.
As described-above, in the method for fabricating phosphor ink in accordance with the conventional art, because a surface defect layer may be formed on the particle surface of the phosphor, a quantity of light generated in the phosphor may be reduced due to the surface defect layer, and accordingly luminance of a PDP may be lowered.
In the meantime, other phosphor inks according to the conventional art were disclosed in detail in U.S. Pat. No. 6,458,294 and U.S. Pat. No. 5,698,614.